chore: /query-stream endpoint now defaults to auto.offset.reset=latest

[vcrfxia]

Description

Fixes #5586

BREAKING CHANGE: The /query-stream endpoint previously defaulted to using auto.offset.reset=earliest. With this change, the new default is auto.offset.reset=latest, consistent with the /query endpoint and the ksqlDB CLI.

Testing done

Unit and integration tests continue to pass.

There's no test coverage for this default at the moment, since TestKsqlRestApp (used for all integration tests) sets auto.offset.reset=earliest on the server. As a result, the old default was also not tested and there is no testing regression in this PR, though we should consider plugging the gap in the future.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[purplefox]

LGTM but not sure it's a breaking change as we haven't documented the new API yet.

[vcrfxia]

OK, I'll leave the breaking change out of the final commit message then (so it won't appear in the changelog). We should publish docs for the 0.10.0 release, though :)